It may be desirable to perform diagnostics on a capacitive sensor. One example, of performing diagnostics on a capacitive sensor is set forth in U.S. Publication No. 2010/0043531 (the “531 publication”) to Garrard et al.
The '531 publication provides a detector circuit for detecting the presence of a remote capacitive sensor having at least two terminals connected via a protection circuit that includes one or more capacitors. The detector circuit comprises a current supply for changing the charge on the sensor and the protection circuit and a detector for measuring the voltage on one or more of the terminals. The presence of the sensor is determined by changing the charge on the capacitive sensor and the one or more capacitors of the protection circuit in a predetermined manner such that the voltage measurement on the one or more terminals when the sensor is present is significantly different than when the sensor is absent.